Detection: Cisco NVM - Non-Network Binary Making Network Connection

Updated Date: 2025-07-01 ID: c6db35af-8a0e-4b61-88ed-738e66f15715 Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This analytic detects network connections initiated by binaries that are not typically associated with network communication, such as 'notepad.exe', 'calc.exe' or 'write.exe'. It leverages Cisco Network Visibility Module logs to correlate network flow activity with process context, including command-line arguments, process path, and parent process information. These applications are normally used for locally and do not require outbound network access. When they do initiate such connections, it may indicate process hollowing, code injection, or proxy execution, where adversaries abuse a trusted process to mask malicious activity.

Search

 1`cisco_network_visibility_module_flowdata`
 2process_name IN (
 3        "notepad.exe", "write.exe", "mspaint.exe", "calc.exe", 
 4        "addinutil.exe", "cmstp.exe", "dialer.exe", "eqnedt32.exe", "IMEWDBLD.exe"
 5        )
 6NOT dest IN (
 7        "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "100.64.0.0/10", 
 8        "127.0.0.0/8", "169.254.0.0/16", "192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32", 
 9        "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24", 
10        "192.31.196.0/24", "192.52.193.0/24", "192.88.99.0/24", "224.0.0.0/4", "192.175.48.0/24", 
11        "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1"
12        )
13
14| stats count min(_time) as firstTime max(_time) as lastTime
15        values(parent_process_arguments) as parent_process_arguments
16        values(process_arguments) as process_arguments
17        values(parent_process_hash) as parent_process_hash
18        values(process_hash) as process_hash
19        values(module_name_list) as module_name_list
20        values(module_hash_list) as module_hash_list
21        values(dest_port) as dest_port
22        values(aliul) as additional_logged_in_users_list
23        values(dest_hostname) as dest_hostname
24        by src dest parent_process_path parent_process_integrity_level process_path process_name process_integrity_level process_id transport
25
26| `security_content_ctime(firstTime)`
27
28| `security_content_ctime(lastTime)`
29
30| table
31  parent_process_integrity_level parent_process_path parent_process_arguments parent_process_hash
32  process_integrity_level process_path process_name process_arguments process_hash process_id
33  additional_logged_in_users_list module_name_list module_hash_list
34  src dest_hostname dest dest_port transport firstTime lastTime
35
36| `cisco_nvm___non_network_binary_making_network_connection_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco Network Visibility Module Flow Data	Network	`'cisco:nvm:flowdata'`	`'not_applicable'`

Macros Used

Name	Value
cisco_network_visibility_module_flowdata	`sourcetype="cisco:nvm:flowdata"`
cisco_nvm___non_network_binary_making_network_connection_filter	`search *`

cisco_nvm___non_network_binary_making_network_connection_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1055	Process Injection	Defense Evasion
T1036	Masquerading	Privilege Escalation

Exploitation

DE.AE

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

This search requires Network Visibility Module logs, which includes the flow data sourcetype. This search uses an input macro named cisco_network_visibility_module_flowdata. We strongly recommend that you specify your environment-specific configurations (index, source, sourcetype, etc.) for Cisco Network Visibility Module logs. Replace the macro definition with configurations for your Splunk environment. The search also uses a post-filter macro designed to filter out known false positives. The logs are to be ingested using the Splunk Add-on for Cisco Endpoint Security Analytics (CESA) (https://splunkbase.splunk.com/app/4221).

Known False Positives

Rare cases may exist where these binaries are used by plugins or third-party extensions to initiate outbound communication. However, such behavior is extremely uncommon and should be investigated for potential injection or abuse.

Associated Analytic Story

Cisco Network Visibility Module Analytics

Risk Based Analytics (RBA)

Risk Message:

The host $src$ observed $process_path$ initiating a network connection to $dest$ over port $dest_port$, which is highly unusual

Risk Object	Risk Object Type	Risk Score	Threat Objects
src	system	40	process_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`not_applicable`	`cisco:nvm:flowdata`
Integration	✅ Passing	Dataset	`not_applicable`	`cisco:nvm:flowdata`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1